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PROTEASE SECRETED BY THE INFECTIVE LARVAE OF ANGIOSTRONGYLUS CANTONENSIS AND ITS ROLE IN THE PENETRATION OF MOUSE INTESTINE

The infective third-stage larvae of Angiostrongylus cantonensis secrete a proteolytic enzyme that is thought to be essential for both larval penetration into the intestinal wall of the host and full development. Protease activity in these larvae during culture in vitro was determined by zymography, pH optimum, and substrate and inhibitor specificity. Excretory-secretory (ES) products of the third-stage larvae showed protease activity as three bands with molecular masses of 66, 30, and 23 kD by gelatin zymography. The optimal pH value for this protease activity was 10.0. The protease was found to have collagenolytic as well as elastinolytic activity, but these activities were inhibited by serine protease or metalloprotease inhibitors. The importance of this protease in larval penetration of the intestinal wall and entering the blood stream was observed in vitro by cocultured third-stage larvae of A. cantonensis with specific protease inhibitors in the intestines of BALB/c mice. The penetration rates of larvae significantly decreased when serine protease or metalloprotease inhibitors were added to the intestines. These results showed that serine protease and metalloprotease in ES products of A. cantonensis third-stage larvae are associated with larval penetration of the intestinal walls of mice.

Received June 28, 2004. Accepted for publication December 16, 2004.

Acknowledgments: We thank L. Y. Chuang and S. G. Yang for their help in assaying the in vitro penetration of excised intestinal wall of A. cantonensis infective larvae.

Financial support: This study was supported by grant no. NSC-85-2331-B-037-015 from the National Science Council, Taiwan, Republic of China.

Authors’ address: June-Der Lee and Chuan-Min Yen, Department of Parasitology, Kaohsiung Medical University, No. 100 Shih-Chuan 1st Road, Kaohsiung City, Taiwan, Republic of China, Telephone: 886-7-312-1101-2169, Fax: 886-7-321-8309, E-mail: chmiye{at}kmu.edu.tw